Cooling a Trading Floor's Data Center

When the Bank of Montreal, Ontario (BMO) recently expanded its U.S. operations with a new trading floor and associated data center in Chicago's downtown Harris Bank building, the company needed to create a reliable, 24/7 mission critical environment where operations were as efficient as possible in order to promote both energy conservation and the health and comfort of occupants.

Three 50-ton modular chillers were specified to satisfy the 100-ton cooling requirement of the data center and electrical equipment rooms. With the specification of modular chillers and because BMO's build-out occupies floors 35 to 37 and the building's mechanical room is located on floor 38, the additional chillers could be brought up through the elevators and installed in the mechanical room directly atop the space they serve.

In the event of an electrical outage, BMO required that data processing support remain uninterrupted for a minimum of 60 minutes, while telecom systems maintain operation for 120 minutes. Complicating the situation, generator backup was not available and the existing building could not support a new generator installation. In order to meet uptime needs, a thermal storage ice tank was specified.

The thermal storage system engages at the prompt of the building management system. Operating on UPS power itself during an outage, the system will open a diverting valve to bring the ice tank into the system loop to directly operate as the chiller. The ice within the system is on a regeneration schedule based on its percentage capacity. When called upon, the chiller plant switches into ice-making mode to re-generate and then switches back. The tank is well insulated, resulting in an overall decay rate of less than 0.1 percent per day.

Other innovative solutions employed to meet BMO's power density and efficiency needs within an older high-rise include: a waterside economizer via closed-circuit fluid cooler, using variable flow condenser water to quickly and reliably transition out of waterside economizer operation, and using the building's medium-pressure ventilation loop as an emergency air dump system.